Polycarbonate is a type of thermoplastic resin, which is a polymer of Bisphenol A, and is widely used as an engineering plastic material which exhibits superior impact resistance, electrical properties and moldability, maintains physical properties within a wide temperature range and has self-extinguishability. Such a polycarbonate resin has been generally used as a housing for small electrical and electronic products such as cellular phones or notebooks.
However, in recent years, a polycarbonate resin is hard to use in housings of electrical and electronic products which are reduced in size and become complicated, since it has a disadvantage of low processability. In order to solve this problem, a polycarbonate resin is blended with other kinds of resin. For example, when a polycarbonate resin is blended with a common rubber-modified styrene-based graft copolymer, the blended resin has improved processability and maintains high impact strength.
Polycarbonate blend resin has generally been used for computer housings, office machines and the like. However, recently, the polycarbonate blend resin is molded into large products emitting great amounts of heat, such as TVs. For this reason, the polycarbonate blend resin should maintain high mechanical strength and have flame retardancy.
In order to secure flame retardancy, a halogen-based compound and an antimony compound have conventionally been used as flame retardants. However, the halogen-based compound disadvantageously causes generation of gases harmful to human during combustion of final molded articles. Accordingly, a predominant method for securing flame retardancy without using a halogen-based compound is to use a monomer- or oligomer-type phosphate ester compound as a flame retardant.
In addition, in order to improve hardness, glass fiber is added as a reinforcing agent. Glass fiber deteriorates flowability and impact resistance, which is an advantage of polycarbonate, and has a difficulty of securing clear appearance due to glass fiber protruding from the surface of the resin.
Many methods for improving appearance qualities of polycarbonate blend resin in order to solve these problems have been devised, but most of these methods are not sufficiently effective.
In this regard, inventions associated with a resin composition, which prevents deterioration in flowability and impact resistance in spite of adding glass fiber so as to improve hardness, exhibits clear appearance during molding, maximizes advantages of a polycarbonate-based blend resin and minimizes disadvantages thereof, remain unsolved.